Thermoplastic resin-graft polyblend compositions

ABSTRACT

THERMOPLASTIC RESIN COMPOSITIONS PREPARED BY BLENDING GRAFTPOLYMERS FORMED OF RUBBERY COPOLYMERS OBTAINED BY COPOLYMERIZING A VINYL MONOMER WITH AT LEAST ONE COMPOUND SELECTED FROM THE GROUP CONSISTING OF ACRYLIC AND METHACRYLIC ESTERS OF TETRAHYDROFURFURYL ALCOHOL, ETHYLENE GLYCOL MONOMETHYL ETHER AND 3-METHOXYBUTANOL, AND AT LEAST ONE COMPOUND SELECTED FROM THE GROUP CONSISTING OF AROMATIC VINYL COMPOUNDS, VINYL CYANIDES, AND MIXTURES OF EITHER OF SAID TYPES OF COMPOUNDS AND MONOMERS COPOLYMERIZABLE THEREWITH, WITH POLYMERS SEPARATELY PREPARED FROM AT LEAST ONE COMPOUND CONSISTING OF EITHER OR COMBINATION OF SAID AROMATIC VINYL COMPOUNDS AND VINYL CYANIDES.

us. or. 250-329 TH];RIYIOPLASTIC RESIN-GRAFT POLYBLENI COMPOSITIONS'Shuji Yoshida, Chiba, and Tateo Iguchi, Ichihara, Japan, assignors toDenki Kagaku Kogyo Kabushiki Kaisha,

Tokyo, Japan 1 No Drawing. Filed Feb, 22 1973, Ser. No. 334,702 Claimspriority, application Japan, Feb. 26, 1972,

' Int. Cl. C081? 41 /'12, 29/56 6 Claims .vinyl cyanides. 1

This invention relates to thermoplastic resin compositions havingprominent weatherability, high impact :stren-gth'and good moldability..

In'recent years, great demand has been made for thermoplastic resincompositions displaying prominent weatherability, high impact strengthand satisfactory m'oldability' even when they are used as electric ormechanical parts in a 'state'exposed to severe environmental conditions.To date,,however, there has not been developed any resin'product'whichcan fully meet the above- 'mentioned requirements.

" There will now be described the studies which have hitherto been madeon thermoplastic resin compositions capable of presenting excellentweatherability, high impact'strength and good moldability. For example,acrylonitrile-styrene copolymers (hereinafter referred to as AS)- andpolystyrene (hereinafter referred to as PS) which present a low impactstrength, though these resins themselves have excellent properties, havebeen denatured for high impact strength into rubbery substances ofconjugated diene series such as butadiene polymer or styrene-butadienerubber (hereinafter referred to as -SBR and accepted in wide fieldsunder the name of ABS or HI-PS (high impact polystyrene). However, saidABS and HI-PS have an extremely low weatherability.

'Thisoriginates with the fact that butadiene series rubber attempts havefailed toenable the resins constituting said compositions to retaintheir original properties due to deterioration when the compositions areused long out of, doors. To obtain prominent weatherability essentially,therefore, it has been proposed to replace the above-mentioned rubbersof conjugated diene series by other rubbers free from unsaturated bondsand displaying good weatherability by themselves, such asethylene-propylene rubber (hereinafter referred to as EPR),ethylene-vinyl acetate copolymer rubber (hereinafter referred to asEVA-) orrubber .of acrylic ester series (hereinafter ,referred to.asnACR).

United, W P te 0.

3,830,873 I I Patented Aug-.29

methyl methacrylate which are desired to have high impact strength.Therefore, EPR, EVA and ACR haveto be graftpolymerized in advance with asuitable monomeric component which is essentially compatible with saidhard brittle resins. In fact, however, EPR, EVAor ACR constituting abase polymer is already saturated, so that the molecules of said basepolymer have very few active points for grafting with said monomericcomponent, obstructing sufiicient grafting. Therefore, a graftpolymer ofmay be EPR, EVA and ACR with said monomeric component presents greatdifiiculties in imparting high impact strength to the aforesaid brittleresins such as AS and PS due to the insufficient compatibility of any ofEPR, EVA and ACR with the aforesaid monomeric component.

Attempts have been made to improve the activity of saturated rubberssuch as EPR, EVA and ACR with respect to graftpolymerization. Some ofthe attempts consist in, for example, growing peroxides in the moleculesof a base polymer by oxidation before graftpolymerization is commenced,introducing a new polymerizable double bond group into the molecules ofthe base polymer or treating said base polymer with radiation. All theseprocesses represent pretreatments preceding graftpolymerization and areintended to increase active points for graftpolymerization on the basepolymer, largely affecting the physical properties of a finalgraftpolymerized product. Therefore, said processes are subject tovarious limitations with respect to the environments and conditions inwhich said processes are carried out, and technically very muchcomplicated. Moreover, these additional pretreatments eventually resultin high production cost.

On the other hand, the Japanese Patent Publications Nos. 33,193/70,1,376/72 and 11,826/72 set forth a method of first preparing a basepolymer by copolymerizing acrylic esters of C -C alcohols withcycloalkenyl esters and then producing a graftpolymer by radicalpolymerization of said base polymer with, for example, an aromatic vinylmonomer. However, none of the abovementioned methods distinctlydisclosed whether the product could display prominent weatherability andhigh impact strength. In addition, the Japanese Patent Publications Nos.8,987/70 and 17,472/62 and US. Pat. No. 3,275,712 indicated descriptionon the production of resin compositions having excellent weatherabilityand impact strength using methods similar to those shown in the firstgroup of patents. The latter group of patents gave suggestions neitheron the resolution of the previously mentioned drawbacks nor on any ofthe conventional processes of manufacturing resin compositionsdisplaying such desired properties.

One of the prior art processes consisted in graftpolymerizingacrylonitrile and styrene with, for example, polybutyl acrylate inthestate of latex. The present inventors tested said process undervarious conditions. However, a resin composition obtained did notpresent high impact strength. This invention has been accomplished toeliminate the shortcomings of all the aforementioned proposed processesand is intended to provide thermoplastic resin compositions displayingexcellent weatherability, impact strength and moldability. Thisinvention comprises thermoplastic resin compositions prepared by thesteps ofcopolymerizing 0.5 to 25 parts by weight of at least onecompoundselected from the group consistingof acrylic and methacrylic esters oftetrahydrofurfuryl alcohol, ethylene glycol monomethyl ether and3-methoxybutanol with 99.5 to 75 parts by weight vof monomers consistingof alkyl acrylate wherein the alkyl group has 2 to 18 carbon atoms toobtain a rubbery copolymer A which is the same as the aforesaid basepolymer; graftpolymerizing parts byweig ht of rubbery copolymer A with100 to 300 parts'by Weight of at'lea'st one'compound selected from thegroup consisting ofaromatic vinyl compounds, vinyl cyanides and mixturesof either of said both types of compounds and monomers copolymerizabletherewith in the'presenceof to 0.5 parts by weight of a chain transferreagent to obtain a graftpolymer B; and blending said "graftpolymer Bwith a polymer C separately prepared from at least one compoundconsisting of either or combination of aromatic vinyl compounds andvinyl cyanides so as to cause said graftpolymer B to be uniformlydispersed in particle sizes of 150 to 1000 millimicrons in said polymerC. Thermoplastic resin compositions of this invention are prepared byeffecting reactions in the following three steps.

Step I: 0.5 to 25 parts by Weight by at least one compound selected fromthe group consisting of acrylic and methacrylic esters oftetrahydrofurfuryl alcohol (abbreviated as THF), ethylene glycolmonomethyl ether (abbreviated as MOE) and 3-methoxy butanol (abbreviatedas MOB) are copolymerized with 99.5 to 75 parts by weight of a vinylmonomer consisting of alkyl acrylate wherein the alkyl group has 2 to 8carbon atoms to obtain a rubbery copolymer A;

Step II: 100 parts by weight of said rubbery copolymer A aregraftpolymerized with 100 to 300 parts by weight of at least onecompound selected from the group consisting of aromatic vinyl compounds,vinyl cyanides and mixtures of either of said both types of compoundsand monomers copolymerizable therewith in the presence of 0.5 part byweight or less of alkyl mercaptan as a chain transfer reagent to obtaina graftpolymer B;

Step III: Said graftpolymer B is uniformly dispersed in 150 to 1000millimicron particles in a hard brittle polymer C separately obtainedfrom at least one compound consisting of either or combination ofaromatic vinyl compounds and vinyl cyanides.

Referring to Step (I, the rubbery copolymer A readily admits ofgraftpolymerization without using any pretreatment required in the priorart and in consequence under the same conditions as in the ordinarygrafting process applied in the manufacture of ABS resin. Said ordinarygrafting process is set forth in the U.S. Pat. No. 3,168,593.

Said ordinary grafting process indeed enables the rubbery copolymer Aobtained in Step I to be fully copolymerized with a compound which iscompatible with PS and AS which are desired to have high impactstrength, and causes the interfaces of the particles of the rubberycopolymer A to have a close afiinity with polymer C. Accordingly theresultant composition indicates extremely good moldability to provide avery gloss product. In fact, however, application of said graftingprocess alone has been found insuflicient to impart high impact strengthto molded articles. The present inventors further study on this pointshows that resin compositions can not be furnished with high impactstrength, unless the graftpolymer B obtained in Step II is uniformlydispersed in the hard brittle polymer C in larger particles than 150millimicrons on the average. Where the graftpolymer B has a particlesize exceeding 1000 millimicrons, then the molded product will decreasein gloss. Therefore the particle size of the graftpolymer B should fallwithin the range of 150 to '1000 millimicrons, or preferably 200 to 800millimicrons. In this case, said particle size need not always beuniform. Where, however, the particle size has an ununiformdistribution, it is necessary that the respective particles should onlydiffer in size by less than one micron. 'I'he rubbery copolymer A usedin the method of this invention should include 0.5 to 25 parts by weightof an adrylic or methacrylic ester of THF, MOE or MOB or a mixturethereof.

The ester of alkyl acrylate (where the alkyl group has 2 m8 carbonatoms) constituting the other component of the rubbery copolymer A mayinclude other copolymersb monomers sh a en ac ylo i le Y n l er andesters of alkyl methacrylate such as methyl methacrylate and2-ethylhexyllmethacrylate, insofar as the glass transition temperature(abbreviated as Tg) of the rubbery copolymer A doesnotexceed l0 C. Wheresaid glass transition temperature. increases oven-1; l0, -C., then theresultant resin composition will noticeably decrease in impact strengthat a lower temperature than Df C. Accordingly, theTg should be lowerthan "-10 or preferably 30 C. Further, if required,=it is possible toadd 1% or less of polyfunctional compounds capable of cross linking suchas divinyl benzene and dimetliacrylate.

Dispersion of the graftpolymer B in the polymer C in particle sizes of150 to 1000 millimicrons can be practically carried out by bringing theoriginal copolymer A to a latex form having theprescribed particlesi zesof 150 to 1000 millimicrons by emulsionpolymerizatio'n. Formation of alatex copolymer having such large particle size can be effected by thecustomary process of making a-coridensed rubbery latex of polybutadieneseries. 1

The graftpolymer B is prepared by graftpolymerizing parts by weight (insolid form) of the latex copolymer A with 100 to 300 parts by weight ofat least one compound selected from the group consisting of aromaticvinyl compounds, vinyl cyanidesand mixtures of either of said both typesof compounds and monomers copolymeriza'ble therewith by means of radicalpolymerization in the presence of 0 to 0.5 part by weight of a chaintransfer reagent. In this case, addition of less than 100 parts byweight of said mixtures of either of the aforesaid both types ofcompounds and monomers copolymerizable therewith is not sufiicient toimpart desired properties to a final resin composition. An optimumaddition of said mixtures ranges between and 200 parts by weight.Further, addition of a chain transfer reagent consisting of alkylmercaptans such as tert-lauryl mercaptan is chosen to be 0 to 0.5 partby weight, but preferred to fall within the range of 0 to 0.3 part byweight. It is practically advantageous to carry out graftpolymerizationby emulsion polymerization.

A compound grafted to the rubbery copolymer A is preferred to be atleast one compound selected from the group consisting of 20 to 100% byweight of aromatic vinyl compounds, 40 to 0% by weight of vinyl cyanidesor 0 to 70% by weight of mixtures of either of said both types ofcompounds and monomers, forexample, methyl methacrylate copolymerizabletherewith.

A group of aromatic vinyl compounds used in graftpolymerization includesstyrene, a-methyl styrene and chlorostyrene, and another group of vinylcyanides used in said copolymerization includes acrylonitrile andmethacrylonitrile. The graft polymer B obtained in Step II which iscompatible with the hard brittle polymer C should preferably be blendedwith said polymer C in willcient proportions to effect fullcompatibility therewith. Said polymer C may consist of the-same type ofaromatic vinyl compounds or vinyl cyanides as those used-in preparingsaid graftpolymer B. r I

The graftpolymer B may be directly blended with the polymer C whichconsists of, for example, PS emulsion, AS emulsion or an emulsion ofa-methyl styrene-styreneacrylonitrile copolymer. The blended mass maylater, be solidified with addition of inorganic salting out reagents. Orit is possible first to coagulate the graft copolymer B with addition ofa proper reagent and then blend said copolymer B thus coagulated withthe separately prepared polymer C on a roll or by an extruder. Whererequired, additives such as a stabilizer and pigment may be incorporatedin the mass in carrying out said blending.

A thermoplastic resin composition prepared by the abovementioned methodof this invention displays very prominent weatherability, impactstrength and moldability and is adapted for application in wide fieldsand, par ticularly due to excellent weatherability, most suitable asEXAMPLE 1 (1) In an autoclave with an agitator were charged 450 g. ofbutyl acrylate, 50 g. of THF, 2.5 g. of an emulsifier (manufactured byKao Soap Company under a trademark Emal #0), 0.1 g. of potassiumpersulfate as a polymerization catalyst and 200 g. of water. The air inthe autoclave was fully replaced by nitrogen gas and polymerization wascarried out at 50 C. When the conversion reached to 40%, 300 g. of waterwas further added. Later the polymerization attained a degree of 98% in6 hours and the average latex particle size was 350 milsize of 80millimicrons. When said latex graftpolymer was further treated in thesame manneras in Example 1 the product indicated an Izod impact value of2.5 kg.-cm./ cm., proving that the product had its properties noticeablyaifected by such a small particle size as 80 millimicrons.

EXAMPLE 2 Polymerization was carried out in the same manner as inExample 1, excepting that the rubbery latex copolymer obtained in Step 1of Example 1 consisted of components having the proportions given inTable 1 below, in which the unit is part by weight. Treatments of Steps2 and 3 were conducted in the same manner as in Example 1. A resincomposition obtained showed the properties whose measured values aregiven in Table 2.

TABLE 1 Butyl MOE MOB THF acrylate 2-ethylhexyl aerylate 2-ethy1eneAerylo. hexyl Styrenenitrile methaerylate Controls.

lirnicrons. NVhen observed by an .electronic microscope, said latexconsisted of particles whose sizes widely extended over a range of 150to 900 millimicrons.

(2) 200 g. of said latex copolymer, 1 g. of Emal #0 and 0.3 g. ofpotassium persulfate were introduced into an autoclave with anagitatorhaving the air therein previously. "ioge gasi Further, 600 g. ofwaofJIZO; g. of styrene, 60 g. of

.13.. wad rs; aetylqnitrileianditl g. tert lauryl mercaptan was addedcontinuously in-twohours; at 60;.(;. so as to obtain concentration of*solidssupon completion of graftpolymerizat'ion. The later wascoagulatedby the addition of 2 000 g. "of-10% caC'l aqCand' the mixture was heatedto 9:0 It as filtered andwashed repeatedly with water nd drie 03.9

(3)i.'I 'here"jwas separately prepared by suspension polymerizatjonresin. containing 30% acrylonitrile and having a total-molecular weightof-100,000. The AS resin was blend'ed onthe roll attl70j. C. with thepowdered "*r jrs ian .L006 I ontinued' for hours at"'"C."1K latxgrai Iob tained particle v properties.

TABLE 2 Tensile Elongation Impact strength at at break Sample strength,yield point, point, Melt index, number kg-cmJcmJ kgJmma b percent bg./10 min.-

I ASTM-D256.

e ASTM-D1238, excepting that the load was 5 kg. and the temperature was250 0.

Controls.

Moldings. obtained from Samples 1 to .9 presented a good --appearanceand gloss,;whereas moldings derived;

i from Samples 10 to .12 were less ,lustrous and, when annealed,contracted themselves-asmuchas to lose their original; forms, and,further as seen from Table 2, promi nently dec ieased in impact strengthand other. mechanical Emitter Resin compositions listedsiniTable 3 belowwere prepatedjinitliefsa'rfie 'fiaiineiasiii'Exanipie' l aise-ping thatI i the initial rubbery copolymbr had thesame composition.

as..S.a I.n p1e. 4.oflExample'lfandwthe.arnountsotcompounds beinggrafted and that of tert-lauryl mercaptan were changed. The impactstrength of the resin compositions Obtained m z fll filslh-resultslbeing. given in. Table .33;

in which the unit is part by weight.

TABLE 3 Grafted compounds Impact Sample Rubbery Acrylo- Methtort-Laurylstrength, number copolymer Styrene nitrile acrylate mercaptan kg.cm./em.

Controls.

The above Table 3 clearly shows that Samples 13 to 21 according to thisinvention displayed far higher impact strength than Samples 22 to 25-falling outside of the invention.

EXAMPLE 4 Samples 2, 4, 5, 7 and 9 of Example 2 were tested forweatherability by irradiating carbon arcs thereon using an instrument ofweathering test (manufactured by Toyo Rika Kogyo Kabushiki Kaisha undera trademark WE- 2) at 50 C. and without pouring water over the tester,the results being presented in Table 4.

TABLE 4 NOTE- Th8 commercially available ABS was manufactured by Denkigiigaku l iogyo Ksbushiki Keisha under a trademark Denka ABS As apparentfrom Table 4, the resin compositions of this invention indicated farmore excellent weatherability than said ABS commercially known as DenkaABS GR 3000.

EXAMPLE 5 There were prepared by the customary process a latex ofpolybutylacrylate concentrated at 30% and having an average particlesize of 100 millimicrons and a latex copolymer formed of butylacrylate-5% THF and concentrated to the same extent as the firstmentioned latex and consisting of particles whose size similarlyindicated 100 millimicrons on the average.

300 g. of each latex was mixed with 200 g. of water, 1 g. of sodiumdodecylbenzene sulfonate and 0.3 g. of potassium persulfate. While themixture was stirred in atmosphere of nitrogen gas, 90 g. of styrenemonomer was added in small proportions to complete copolymerization. Themixture of graft-polymer and styrene homopolymer obtained was separatedinto the respective components by fractionation usingmethylethylketone-methyl alcohol.

The results are shown in Table 5.

TABLE 5' v. I on 1 n r i' i it ra poymer omopo ymer 0 pay yrene Typeollntex (percent) (percent) (percent) Copolymerot95% butylacrylate and5% THF.-,.- 81 Y 19 62 Polybutylacrylate 53 47 6 Control.

Table 5 shows that while grafted styrene was only 6% in the case ofpolybutylacrylate, it was 62% in the case of the rubbery copolymer ofthis invention though said copolymer contained only 5% THF, proving thateven if only 5% THF is used as one of the ingredients of the rubberycopolymer, graft elliciency is prominently elevated on account ofnumerous active points on THF. The graft efiiciency was determined asfollows:

Each latex was used in an amount of 300 g., at 30% concentration and ina state containing g. of solids. 90 g. of styrene was used as a graftmonomer. Therefore, the rubbery copolymer and the styrene monomerrespectively amounted to 50% of the mass used in said determination.

Graft Efficiency 81 50 (this invention) 5 Graft Efficiency 53 50 What weclaim is: f p 1. Thermoplastic resin compositions prepared by the stepsof copolymerizing 0.5 to 25' parts by weight of at least one compoundselected from the group consisting of acrylic and methacrylic esters oftetrahydrofurfuryl alcohol with 99.5 to 75 parts by weight of monomersconsisting of alltyl acrylate wherein the alkyl-group has. 2 to 8 carbonatoms to obtain a rubbery copolymer A; graftpolymerizing 100 parts byweight of said rubbery co polymer A with 100 to 300 parts by weight ofat least one compound selected from the group consisting of aromaticvinyl compounds, vinyl cyanides and mixtures of either of said bothtypes of compounds and monomers copolymerizable therewith in thepresence of0 to 0.5 parts by weight of a chain transfer-reagent toobtain a.graftpolymer B; and blendingv said graftpolymer B- with..apolymer C separately prepared from at least one compound consisting ofaromatic vinyl compounds, vinyl cy: anides and mixtures thereof so asltocause said graft; polymer B to be uniformly dispersed in particle sizesof to 1000 millimicrons in said polymer'CQ' 2. Resin compositionsaccording to claim 1 wherein the vinyl monomers partly constituting the"rubbery c'o'- polymer A are prepared by incorporating in the alkylacrylate at least one compound selected from the group consisting ofstyrene, acrylonitrile, vinyl ethers and methacrylic esters, insofar asthe glasstransition temperature of said rubbery copolymerA-does notexceed +10 C. 1 3. Resin compositions accordingto claim lzwherein thearomatic vinyl compound is at; least one,compound selected from thegroup consisting of styrene, l ta -methyl styrene and chlorostyre'ne','an'd the VinyLcyanide is at I least one compound selectedfr'omflthe'gr'oup consisting of acrylouitrile and methacrylonitrile."

4. Resin compositions according to claim 1 wherein one of the monomerscopolymerizable with either of the aromatic vinyl compounds and vinylcyanides is a methacrylic ester.

5. Resin compositions according to claim 4 wherein 75 the methacrylicester is methyl methacrylate.

6. Resin compositions according to claim 1 wherein said compoundgraftpolymerized with the rubbery copolymer A is 20 to 100% by weight ofaromatic vinyl compounds, 40 to 0% by weight of vinyl cyanides and 0 to70% by weight of mixtures of either of said both types of compounds andmonomers copolymerizable therewith.

References I Cited UNITED STATES PATENTS 3,632,684 1/1972 Tellier et a1.260-88l 3,517,084 6/1970 Tellier et a1. 26088l PAUL LIEBERMAN, PrimaryExaminer US. Cl. X.R.

